Wachusett Aqueduct
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 Wachusett Aqueduct at Northborough |
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| Official name | Wachusett Aqueduct |
|---|---|
| Begins | Wachusett Reservoir |
| Ends | Weston Reservoir |
| Maintained by | MWRA |
| Length | 9 mi (14.48 km) |
| Conduit height | 11 ft (3.35 m) |
| Conduit width | 12 ft (3.66 m) |
| Capacity | 400 ft³/sec (11.32 m³/sec) |
| Construction began | 1897 |
| Opening date | 1905 |
| Geographical Data | |
| Coordinates | |
The Wachusett Aqueduct carries water from the Wachusett Reservoir to the Weston Reservoir. It is part of the Boston, Massachusetts public water supply system, maintained by the Massachusetts Water Resources Administration (MWRA).
Contents |
[edit] Tunnel Dimensions
The tunnel has the following characteristics:
- Width: 12 ft (3.66 m)
- Height: 11 ft (3.35 m)
- Length: 9 mi (14.48 km)
[edit] Physical Characteristics
Water from the Wachusett Reservoir flows through the Wachusett Aqueduct to the Weston Reservoir. The Wachusett Aqueduct extends from the Wachusett Reservoir in Clinton, through Berlin to Northborough, Massachusetts. This 9 mile-long (14.48 km) water system consists of 2 miles (3.22 km) of hard rock tunnel and 7 miles (11.26 km) of 11 ft-high (3.35 m) horseshoe-shaped underground aqueduct constructed of non-reinforced concrete with a brick-lined invert. It is not constructed entirely underground and there are several elevated over crossings, one of the most picturesque being the Assabet River conduit in Northborough, shown here.
[edit] Novelty
Until the 1960s, the Wachusett Aqueduct was the main conduit used to deliver water from the Wachusett Reservoir. At that time, it carried 300 million gallons of water each day. The Cosgrove Tunnel replaced it in 1965 at the primary water transmission aqueduct. Because of the construction of the water treatment facility at Walnut Hill, the Cosgrove Tunnel was shut down in 2003 in order to make the large piping connection between the new treatment plant and MWRA’s new MetroWest Water Supply Tunnel. The MetroWest Tunnel extends east 18.6 miles (29.92 km) from Walnut Hill to Weston. During that shutdown, the Wachusett Aqueduct was the primary method of transmission of about 240 million gallons (908 million liters) of water per day. It remains a backup connection to underground storage near the Massachusetts Turnpike in Weston.
[edit] MWRA water system overview
The MWRA and the Massachusetts Department of Conservation and Recreation (MDCR) own and operate the collection, treatment, distribution, and storage facilities that supply drinking water to some forty municipalities in the metropolitan Boston area. This water system design was based upon the purchase and subsequent protection of an entire watershed. This design assures that the water remains as pristine as possible. However, modern regulations require that all supplies of drinking water be chemically treated regardless of the source[1]. Additions to the MWRA water system throughout its history have resulted in redundancies that allow major sections of the water system to be shut down for repair or maintenance.
[edit] Water flow
Water flows from the MWRA's main storage facility, the Quabbin Reservoir in central Massachusetts, through the Quabbin Aqueduct to the Wachusett Reservoir in and around Boylston and Clinton [2]. Tributary rivers and streams comprising the Wachusett watershed, a 108 square mile (280 square kilometer) drainage basin, also feed the Wachusett Reservoir. At the eastern end of the Wachusett Reservoir, water enters the Cosgrove Tunnel at the Cosgrove Intake. The Cosgrove Tunnel feeds both the MetroWest Water Supply Tunnel (MWWST) and the Hultman Aqueduct. The MWWST starts from the Carroll Water Treatment Plant in Marlborough. The Hultman branches off at Framingham in two directions. The smaller branch, the Weston Aqueduct, empties into the Weston Reservoir in Weston. The main branch continues to the Norumbega Reservoir, also located in Weston[2].
[edit] Redundancy
Water can be treated with chlorine as it leaves the Wachusett Reservoir in an emergency, and again as it leaves the Norumbega Reservoir. This is to provide for a backup to the new water treatment facility, the John J. Carroll Water Treatment Plant, which started operation on July 27, 2005[3]. This plant is of modular design and provides ozonation for primary disinfection, chloramination for residual disinfection, fluoridation, and pH control.
[edit] John J. Carroll water treatment plant
Located at the town lines of Marlborough, Northborough, and Southborough, Massachusetts, this facility replaces the one used previously only for pH control[4]. It comprises four ozone generators with diffusers and five concrete contact chambers with a volume of 11.3 million gallons (42.7 million liters). The plant has a capacity of 275 million gallons (1.04 billion liters) per day, on an average day or 405 million gallons (1.53 billion liters) per day, at peak level. It cost US$340 million[3].
[edit] Electrical generation
The system includes three hydropower stations, with a total capacity of 8 MW[5]. Water released to the Swift River flows through the turbines at Winsor Station below the Winsor Dam. Water transferred from Quabbin to Wachusett can pass either through the turbines at Oakdale or through bypass pipes when flow requirements exceed turbine ratings. Water released from Wachusett into the Cosgrove Tunnel passes through the Cosgrove turbines[2][3].
MWRA power generation
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The Quabbin Aqueduct connects the two reservoirs, and relies upon gravity to accommodate the three separate operational needs. First, diversion of water from the Ware River into the Quabbin Reservoir uses this aqueduct. Second, water transfer from the Quabbin Reservoir to the Wachusett Reservoir, through a hydropower station or a bypass pipe, uses it as well. The bypass valves are non-regulating valves, and when opened, only the head in the Quabbin Reservoir and the physical characteristics of the aqueduct govern the flow. Because the turbines are flow limited, the bypass mechanism permits transfer rates nearly twice as high as are possible through the turbines. Operationally, the single aqueduct fulfills three purposes, but only one operational mode is possible at a given time [6].
[edit] MWRA references
- ^ Safe Drinking Water Act. Retrieved on 2006-12-01.
- ^ a b c MWRA water system. Retrieved on 2006-12-01.
- ^ a b c Water system history. Retrieved on 2006-12-01.
- ^ John J. Carroll water treatment plant. Retrieved on 2006-12-01.
- ^ Electrical power generating plants. Retrieved on 2006-12-07.
- ^ Water system configuration. Retrieved on 2006-12-01.
[edit] References
- Metropolitan Boston water system history
- Aqueduct over-crossing on State Route 20
- Legal brief by the United States Army Corp of Engineers
- March 19, 2001 start of Wachusetts Aqueduct rehabilitation
- EPA permit to discharge effluent while repairing the Wachusetts Aqueduct
- Some details of the aqueduct’s construction and repair
- Court order and statement of facts about MWRA facilities
